Making the Case for Vertical Axis Wind Turbines

The marketplace is littered with the remains of companies that have tried to make a success of vertical axis wind turbines (VAWTs). So much so that conventional wisdom has it that something must be wrong with the technology itself; otherwise, there would be successful companies in this space.

But let's review some history. During World War II, Western nations spent vast amounts of money improving the design of propellers for aircraft, while VAWTs got nothing. Much of the money for propeller development went to large companies. Some of these companies took the technology and made large windmills. So we have a situation where a well-funded technology was adapted by well-funded companies. It should not be a surprise that these have been successful.

In general, the wind industry has been successful primarily due to subsidies. Since large companies pay lobbying groups to support these subsidies, these companies have continued to do well.

Compare this to the largely unfunded or underfunded small groups, which lack the talent and resources to undertake a truly competitive VAWT development effort. Since large-scale turbines cost millions to prototype, it is no mystery why nearly all the VAWT development efforts have been on a small scale.

With regard to small-scale horizontal axis wind turbines (HAWTs), it is not reasonable to take performance data from multimillion-dollar machines and say that a scaled-down, much cheaper version will give the same performance. In fact, data from the CADMUS Group showed that the performance of small HAWTs was nowhere close to promotional claims. In fact, on average the power output was about one-third of that projected. In the small wind sector, claims about the superior performance of the HAWT vs. the VAWT need to be carefully considered.

Large wind turbines, carefully sited to take advantage of strong and highly directional wind flows, achieve very good efficiency figures, but the results from these expensive machines simply cannot be applied to any HAWT located in a less than ideal site. Far too often, overzealous marketing outweighs good engineering when it comes to small wind turbines.

For most small wind turbines, the location is selected not because there is a good wind resource, but due to the buyer's need to obtain power from the wind resource at a specific location. This means that most small wind turbines are installed in suboptimal wind locations. Small wonder that the performance is well below the utility-scale turbines.

A location where the wind direction is highly variable will result in poor performance for a HAWT, while a VAWT that catches equal power from wind of any compass heading will outperform the HAWT in these locations.

Another feature of industrial-scale HAWTs is their high tip speed ratios (TSRs). There is ample evidence that higher speeds on the windmill blades result in more efficiency, but this efficiency comes at a price. Noise downwind of these turbines has been a major factor for wind farms using these machines. For smaller HAWT units, the noise is of a different sort as the turbine spins up and down and clatters about adjusting to the wind direction. Using a lower TSR, the Wind-Sail VAWT still achieves good performance on a machine that is nearly silent.

Warren, It is certainly true that the logistics of setting up a vertical turbine are a bit less daunting. So if something besides cost is considered they are probably a better choice. It does seem that with only vertical rotating components and no wind-tracking hardware that the mechanism is far better suited for survival situations. And thos wires snagging birds could be a useful source of food. Unintended consequences, you see.

Actually, William, there are two truisms in this article. The other is "overzealous marketing outweighs good engineering." How many times have we had to tell marketing "NO!"

I was very happy to read this report about relative efficiencies of the vertical and horizontal systems. I have been quite interested in pursuing the energy field for survival usage, and the vertical systems solve a lot of problems- portability, footprint, etc. Now I need to find out who has developed the best system for portable use.

Elizabeth's point is important. Apart from efficiency considerations, a big objection to HAWTs is their harm to birds and bats. It seems to me that VAWTs could be more easily shielded or caged so that birds cannot enter the blade path. There has to be a better way to catch wind energy than those view-spoiling propellers. Environmental concerns should be weighted vis a vis effeciency.

Interesting article, and it contained one completely true gem statement:"If you lack the skill and resources to hire talent you will probablynot be successful." That is true in almost everything that depends on capitol and skill to make work. Besides that, it is very poor style to complain about how nobody would support your product development because they were supporting somebody else who was successful.

I am also fairly certain that if the vertical axis wind turbines were able to produce more power for the same price that they would be the dominant type that we would see. But there is no way to fast-talk around the physics of the operation. Putting the generator at ground level would be a real cost-saver, buthavng the turbine shaft extend a hundred feet up has to be an engineering challenge, and keeping the whole thing vertical seems like a challenge as well.But for the home experimentor a vertical axis system would probably be a better choice.

I don't have time to go into detail but too much of this article is wrong.

The reason he didn't put up HAWT data is it would show how wrong he is.

Small wind gens were about prefected in the 30's!! Many are still spinning and making power eff. Really little has been done since then. But they are good and rather hard to get much more because not much more energy left to harvest.

A few things about me, I've designed, built all the kinds of wind generators and sold some in the 80's and presently building a 50kw VAW linear generator, otherwise known as a high speed cruising sailboat/trimaran that will do 25mph on wind, one of many.

I want to make power/money from the wind and can pick any type I want based on output, cost, etc. I can clearly say that VAWT's have little value when you can get 2-5x's more power from a unit of far less weight, thus cost a well done HAWT gives.

Let's have some details on the VAWT shown like weight, swept area, ability to last longer than a month, cost, rated output speed, a decent picture with details, etc. Why did he leave these out? You can't compare without them.

It's rated at 3kw yet only makes 600watts in much higher wind speeds than US average even though his supposed maket he says had worse winds, another dubious point, as trees are far more a problem blocking wind that buildings ever would except in 100th of 1% of US land.

Having my pick of all designs a 14'dia HAWT with semi-variable pitch direct drive alternator with a downwind rotor, not unlike the SWWP Skystream3.7 though fixing it's minor problems, at under $1.5k/kw in 18mph winds. Next yr mine will be out, designed exactly for the urban, suburban market. I can garranty My version will make 2-3x's the power as the one somewhat shown. If he want to compete with me fine but he'll lose big time.

Noise comes from badly designed blade tips. Done right noise is no more than normal wind noise. Higher TSR simply makes more power by basic physics, limiting it to 2.5 just loses eff, output.

The potential benefits of Verical Axis turbines to small / remote locations are clearly stated. It's unfortunate that the article begins by opining that aircraft propeller experience and big business is responsible for the success of HAWT's. The difference in power density and operating regimes makes propeller (or aircraft wing) technology essentially irrelevant to wind turbine design or manufacture or application. I was part of the early industry when NASA spent quite a few years and $'s unintentionally proving that point. I was also deeply involved in the 80's when attempts to scale various VAWT concepts to commercial wind farm size proved unsuccessful. It wasn't for lack of trying or funding or technology.

The success and continuing technology advantage of HAWT's is based on their ability to reach the better and more uniform wind resource at heights of 100 - 200m to become commercially viable. Operation at those heights also changes the noise sensitivity. The same attributes that allow VAWT power train equipment to stay near the gound also effectively limits how high the rotor can go. Another challenge unique to VAWT's is the reversal of wind load on each blade during each rotation; the resulting fatigue caused dramatic failure of several early "large" Darrius machines.

Small scalle HAWT's face the same challenges as small scale VAWT's - a small market with diverse requirements and comparatively limited $ resources. I was disappointed not to find data comparing performance between the VAWT and HAWT machines said to share the site for the purpose of comparison.

There is actually more good news for VAWTs. As the author notes, virtually all the public R&D money has gone to HAWTs. But as at good wind site are filing up, we are need equipment that will take better advantage of what is left. I have been interested in "urban wind" for some time, and have researched how VAWTS might be practical in cities or less windy areas. In particular, McDonnell Douglas did extensive research on a VAWT concept that you never hear much about today. The concept is to control the pitch of the blade as it rotates around the center axis. In this way, the blade can be held near its optimum lift angle of attach through a portion of its rotation. The blade pitching also helps on the downwind side as well. MD designed, built and tested a 40 kw test machine, and was later poised to go much larger when the test results indicated many advantages over HAWTs.

More Recent research has indicated VAWT performance may actually increase when used in a array where neighboring turbines spin in opposite directions. This is a clear no-no for HAWTs but could make wind farms practical on roofs of tall buildings. Also, array logic could make open sea installations more practical as well.

Thnak you for the interesting article. I'm not sure it is accurate to say that modern horizontal wind turbines come directly from WWII government funding. Propellers on airplanes turn much, much faster and in flight engage oncoming air at much higher speeds. My sense is that most of the relevant work has been more recent.

I would like to see the chart for the side-by-side comparison. Perhaps it was removed due to space constraints? Anyway, I don't see a way to comapre efficiencies or output.

I note in your photo that because you have to elevate your vertical turbine to get better wind access, you then need guy wires to support the tower. These have been shown to be very fatal to birds, at least in the Western/mid-Western US. So that is a trade off. Would you say that in a full industrial scale application a larger tower would be used and no wires, or would a guy-wire set up be typical?

Noise is an issue in some cases, but most industrial scale wind farms (again, around Colorado where I live/work) are away from population. The small scale vertical turbines have appeared in back yards where noise is surely one consideration. Unfortunately, one vertical turbine I see nearly every day in Boulder rarely turns; I have watched it since it was first installed a year ago and I have to think it does not come close to claimed generating power. It probably went in mainly due to tax incentives from various government sources.

I think the author has made an excellent case for vertical axis wind turbines. They are multi-directional, allowing them to be placed in locations where the wind direction varies (most locations) and the noise is directed upwards, not disturbing anyone. I'm surprised some company hasn't developed such a machine.

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